Polyurethanes (PUR) containing 37 % of soft segments, obtained by prepolymer chain extension in the reaction of diphenylmethane 4,4′-diisocyanate (MDI) with 1,4-butanediol (1,4-BD) were synthesized. Soft segments of PUR were built either of poly([R,S]-3-hydroxybutyrate) (a-PHB) and polycaprolactonediol (PCL) or a-PHB and polyoxytetramethylenediol (PTMG) (Table 1). The effects of a presence of synthetic a-PHB in the PUR chain on the thermal and mechanical properties, water and vegetable oil sorption and sterilization efficiency of the materials prepared, designed to medical applications, were investigated. It was shown by DSC method that the introduction of a-PHB with methyl side group to the soft segment disturbed phase segmentation leading to glass transition temperature (Tg) shift to higher values (Tables 2, 3). The presence of a-PHB in the chain increases the hydrophilicity of the products, causing better water absorption and lower absorption of vegetable oil (Table 4, Fig. 1). The results of microbiological tests and the mechanical properties of a-PHB containing PUR samples show that such materials can be subjected to plasma sterilization without surface flaw (Table 5) and PUR obtained can be used for medical applications if not high mechanical strength is required.
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Polyurethanes synthesized from biocompatible components were used to produce composites with 5 and 10 wt % chitosan content. The hard segments of polyurethanes were obtained from aliphatic 4,4′-methylene dicyclohexyl diisocyanate and 1,4-butanediol, while the soft segmentswere derived from polycaprolactonediol and synthetic poly([R,S]-3-hydroxybutyrate) in aweight ratio of 90:10 or 80:20. The hardness of polyurethanes and their composites with chitosanwas typical for elastomers used in medicine. DSC thermograms showed that the investigated polymers were semicrystalline. The morphology of their surface observed under optical microscopewas heterogeneous. The presence of chitosan in the composites reduced their water vapour permeability, resulting at the same time in an increased water sorption, while not influencing the oil sorption of polymer samples.
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